Wednesday, July 1, 2009

The First Week in the Pilbara

18th June – Up at 4:30, out of the Mounts Bay Road Lodge after three nights in Perth. A 2 hour QantasLink flight to Newman: one of the three major iron ore mining towns in the Pilbara. After a bit of a wait due to crossed emails, CoreFleet arrived with our Toyota Landcruiser. It lacked spare tyres. Whoops. Off to the CoreFleet motor pool, where a rather embarrassed mecho put a pair of extras on the vehicle. Back to “downtown” Newman, iso a week’s worth a food, camping supplies, and most importantly, a key multi-use tool: the shovel. A Chicken Treat lunch, a gear sort on the footie oval, and off we went into the field.

My first site was the Weeli Wolli Creek area. Bruce and I were first there in 1985: we tried to access the same area in 2007, but the road we’d used to get to the area of interest was almost fully overgrown. I kind of knew where it was, and worried that we would not be able to find it. The dirt road weaved past the Rhodes Ridge exploration camp; a relic from the 1960s. We crossed Weeli Wolli Creek for about the eighth time, and came to the area of the track. There it was; fresh tyre tracks indicated recent use. After a rough bounce, we arrived right at the section I wanted to look at.

First swag out in the Pilbara. Rocky ground; blocky chert talus from the hills I wanted to work on. Sundown, and the stars appeared. Oh, to be able to see this full sky of stars for more than a couple weeks per year. A joy to see the Southern Cross, Scorpio, the Milky Way, the Magellanic Clouds. Chilly, not too cold.

19th June – Up at 6, time to photograph the sunrise. My numb fingers fussed with the tripod and other gear, but I was in plenty of time to make some good exposures. Shoot and learn. My usual breakfast: fruit, more fruit, soy milk, peanuts, a bit of muesli.

Up the hill to the impact layer. Wow, not what I’d expected from a quick look the day before. A thick spherule zone at the base, overlain by a good meter of mass flow (underwater landslide) deposits. Time to start training Louis. Here is how to take my dictation. No, don’t wind up the tape between every section, it wastes time. Please keep me honest when I confuse planar laminations and parallel laminations.

Descending the hill after measurement. I always forget that Hamersley Range hillsides are bloody steep and rubbly. It would be too easy to take a dive off ledge, courtesy of the wrong chunk of loose rock, and fall three or four meters. And probably land in spinifex. I never forget how spiny this grass feels when it sticks me in the hands, legs, knees and butt. I’d never climb a hill like this at home; I guess I’ll do anything for rocks. I look for wallaby trails, they pick the good lines.

The view is worth the treachery of steepness and poky plants. The Weeli Wolli drainage forms a broad valley, punctuated by small buttes of dolomite and the winding course of the stream, outlined by white gum trees.

20th June. I wanted to take Louis to Weeli Wolli Spring, one of the few places in the Pilbara with consistent surface water. It’s about eighteen kilometers north from yesterday’s work area. More dirt road. I like being back in a Landcruiser. It has a tighter suspension than the Nissan we had in the NT. It’s geared lower, and the engine seems to have more juice. A better field vehicle. More fun to drive.

I have also been meaning to comment; this truck, the NT Nissan, every other field truck I’ve had in Aus, and all the mine vehicles have tyres with a narrow tread width. The Cruiser’s are 235s. This is a stark contrast to standard SUV tires in the US, which are much wider. I wonder why – practicality of use vs. appearance? There’s plenty of dirt, mud, rock, and so forth to drive across here, much tougher than asphalt in any country.

We camped at Weeli Wolli Spring last night, by the water. The natural flow has been subsumed by groundwater pumped out the Hope Downs mine; the stream literally roared just a few meters from the campsite. Its good for flowers; I see a new type of creeping violet. It’s not in my plant book.

In the morning, a brief walk along the drainage, above the mine water input. Scattered pools appeared amidst the rubble of the otherwise dry drainage. Weeli Wolli is home to lots of kajput paper bark gum trees. Like most eucalypts, this tree sheds its bark, but instead of coming loose in sheets, it peels away in delicate, paper like layers. They’re white, and look perfect for writing till you touch them and they dissolve. I take some close-ups of peeling bark. My eye is also attracted by the abundant flood debris – from last summer’s cyclone? The broken ruptured shapes of small trees and shrubs wrapped around larger trunks cheers me up. I’m not sure why.

Later in the day, a second work site, at an undisclosed location. See my earlier blog.

21st June. A cold swag out, enhanced by some star track photography. I somehow managed to get the south astronomical pole in just the right place. Good dawn photography on the hill.

Today was ninja day. I knew exactly where I wanted to work, but getting there required either crossing a mine lease without permission or taking an unused road in Karijini National Park. We headed up Route 95. The mine lease road turned off to the left. I equivocated. Intuition said keep going; don’t risk the wrath of Rio Tinto or their surrogates. Another hour in the truck, into Karijini. The park road I wanted to take went past the ranger HQ. I figured what the heck. As we drove in, a ranger was driving out. We waved to each other. I kept going.

Another track in excellent condition. This was formerly the main drag from the Wittenoom-Roy Hill Road through to Newman. It passed several stations and mining camps; Juna Downs, Packsaddle, Rhodes Ridge. We used it extensively before the sealed Rt. 95 came into existence. Again, a track in great shape. I kept expecting washouts, trees growing in the road, or some other hazard. But the track was great. I’d given Louis responsibility for keeping track of our progress on topo and geologic maps. He slowly gets the hang of it.

The road turned east. On our left, a promising section appeared. We parked off the road, geared up, and climbed another hill. After some casting around, I found spherules at the base of a three meter bed. Wow, very thick! Usually it’s about a tenth of this. A cool variation; much of the thickness came from a massive, very muddy bed, probably the settle out of a cloud of mud on the sea floor.

I was happy. We’d snuck into the section, and it was a good one. The work finished, we headed back up the Juna Downs road. I made Louis practice driving a manual transmission. He did fine. Just past the ranger station, the pieces of a wrecked airplane were laid out by the side of the road. It must have crashed and burned nearby, and been reassembled as such here. The light was good; I backed up to take a picture. As we got out the truck, a familiar hiss sounded. Crap, the left rear tyre was going flat. I taught Louis how to change a truck tyre. He did fine. Unfortunately, the spot where we had to change the tyre was about the dustiest area of the road. We were both coated in red dust by the time the new tyre was on.

22nd June - The combination of a flat tyre and personal red dust layering dictated a night at the Auski Tourist Village. Sigh, I’m glad that Auski exists; showers, a mechanic, and clean campground and facilities are nice luxuries. But it’s not the same as camping in bush, with no one around. Auski is also a stop for road trains en route to Newman or Port Hedland. So it’s noisy, bright, and loud. I wasn’t ready for civilization yet. But the shower felt really good.

In the morning, after the tyre was declared healthy, I pointed the Cruiser east towards Roy Hill. I wanted to go to the eastern edge of the outcrop area, where I hoped we could find the impact layer before it dived below the surface of the Fortescue River Valley.

Into the morning sun. A broad, dusty road, fairly dusty, but virtually no traffic. Again, I had a destination in mind: Koodaideri. I have no clue where this name came from; it could be Aboriginal, or butchered English of some sort. Bruce and I were last here in 1986. We drove as far as I could stand it before turning south to the hills. Another quick walk up a steep, rubbly hill. The spinifex was longer here. More time had passed since a burn.

I spied a promising bed above me. It looked like the Juna Downs impact layer; intriguingly and anomalously thick. I climbed straight up the slope at it, over low cliffs, through bushes and spinifex.

The bed was not what I expected. Wow – it was full of boulders! This very unusual in the Hamersley Basin, where mud is the fashionable grain size. I was mesmerized. Oh yeah, look for spherules. Bugger, could not find any in the bed, at all. I looked carefully. Louis looked carefully. None, none at all. Oh well, it was still cool. Many of the boulders in the bed were limestone which showed evidence of forming in shallow water: stromatolites and evaporites were common. Very, very cool. I’d never seen this stuff here before; it outcrops 250 kilometers to the northeast (where the shallow water was 2.5 billion years ago). A couple of the boulders were the size of the Cruiser. Very, very very cool. I am a sucker for giant clasts. This bed had to be a debris flow deposits; a type of cohesive, mud-rich underwater landslide. Looking at these guys is some of my favorite geology. Now if it had only contained impact spherules. Still, a fun discovery.

Late morning, still time to investigate the Koodaideri area. A bit further east, and another track towards the hills. It ended amid the ruins of a good half dozen buildings. Maybe this was the original Koodaideri? It could have been an outstation for one of the grazing operations that were here before the mines came in. All the remained were concrete foundations, bits of wire, and trash. Louis found a broken bottle from a brewer in Wittenoom, the old asbestos mining town sixty kilometers to the west. Wittenoom has been gone for over fifty years. I tried to feel this place. Who lived here? Did they like it? Did they enjoy the lovely Hamersley Range? Did they go to the Fortescue Hotel in Wittenoom to relax on days off? Where are they now?

It was 3:30. No sign of the impact layer, but a good day for seeing cool rocks and touching a bit of the recent past.

The most elusive impact layer in the Hamersley basin is located at the very top of the Jeerinah Formation, well below the spherule layer that’s the focus of this trip. Having given Koodaideri our best look see, I thought it worthwhile to run north across the Fortescue River Valley from Auski, to where the Jeerinah crops out.

Route 95 crosses the very broad Fortescue River valley as it heads towards the equator (it doesn’t get there, to be clear). The Fortescue flows only during floods, I suspect. I’m not even sure when we crossed the drainage per se. All the mulga, gum, and spinifex had a bathtub ring of mud from the last flood; no way to tell exactly where the drainage was.

We ascended out of the valley; a severe climb of at least 15 meters. The landscape here is different. Most of the rock is volcanic; the land looks burnt to a deeper shade of orange than I am used to from the Hamersley Ranges. It looks to support a more meager plant community as well. This might be because it makes for poorer soil, worse drainage, or something else I have not thought of.

It was 5, getting close to time to camp. Louis spied the old dirt road from Wittenoom to Port Hedland; another route supplanted by progress and bitumen. We turned off on it, drove far enough to not be able to hear road traffic, and swaged out.

23rd June. The Jeerinah outcrops were poor. I was able to identify the right stratigraphic interval and locations pretty easily, but the key areas were covered by scree and spinifex. Oh well, we looked. Time to head back to the Hamersley Ranges and the real project.

Lunch in Wittenoom Gorge. As I have probably written in previous years, Wittenoom was an asbestos mining community from the 1930s to the 1960s. It withered once the asbestos market died. The Australian government has been killing the town off since then to discourage visitors. There are no services available, save for a pay phone two kilometers east of town. Almost every building – including the source of the bottle Louis found at Koodaideri – has been torn down. A few holdouts and their private property remain. It’s eerie; I remember when the main street was lined with buildings.

I drove up Wittenoom Gorge to find a nice lunch spot. It’s still beautiful, although the asbestos fibers in the road and chunks of ore in the stream reminded me that it was not a place to linger. The water level in Cathedral Pool, my favorite spot, was quite high. The best lunch spot there was covered in lemon grass. No room to sit; no one had been there in a while.

A partial compensation for the lack of a spherule layer at Koodaideri, we measured a beautiful version of the layer adjacent to Wittenoom’s rubbish tip. Besides a great section, this area had the longest spinifex I’ve seen this trip. Louis hadn’t really had the pleasure of spinifex yet; this was his unavoidable introduction. The only way to move forward was to crash through the spinifex tuffs, take the pain of continual punctures, and wait for one’s legs to go numb.

Wittenoom Gorge is not place to camp. We headed further west to Bee Gorge to swag out. This is another favorite spot. It was a bit challenging this time. While there were plenty of all the usual items needed for a good camp: wood, flat only semi rocky spots to sleep, space to spread out, and a view, there were a couple distractions. First, the ground was alive with small insects. They did not seem interested in our food or in us, but they inevitably crawled onto whatever gear was in contact with the ground. That would be everything. Second, the sky became ominously cloudy. The light dimmed; I knew this meant rain was possible.

24th June – We slept through the bugs. The sky stayed gray. Intermittent drizzle began in the morning. It was a damp breakfast. I did not want to be stuck on a dirt track in any sort of rain. It was time to go to Tom Price.

As we headed out the track to the main dirt road, the showers began. The windshield wipers worked; that was a relief. I drove carefully west and then south through the range front. The rain got heavier, but was still intermittent. It was noticeably cooler; low clouds hit the landmarks I expected to see once we cleared Rio Tinto Gorge. The track was still fairly dry. I was glad to see that we were leaving a dust cloud behind us. Finally, bitumen 60 kilometers from Tom Price. The rain was steady but light.

Tom Price in the rain: another new experience. The Tourist Information Centre predicted rain all day. We shopped. I called my contact at the mine and set up time the next day to work on site. We did internet. One of the Cruiser’s back doors froze shut: probably dust in the mechanism. I pulled the plastic panels off, moved all the wires and stuff around, banged on it, but could not get it to function. Annoying. It rained really hard for 30 minutes – a real downpour. Wet schoolchildren wandered by.

It was time to swag out. Where to go? It was going to be wet wherever we went. I know it would be lower south of town. We drove a bit, found a track, and eventually came to a spot big enough for the truck, two swags, and a cooking spot. It rained. I sat in the truck and read. Louis built a shelter using our tarps and read. It got dark. I cooked. We slept in the increasingly intermittent rain.

Now I’ve seen rain in the Pilbara three times. This was certainly the most intense. Luckily it was congruent with my plans, and more inconvenient than anything else. All my gear is plastic; it dries fast. I discovered that spinifex is quite lovely when it’s wet.

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